Support for detecting thyroid and other pathology in persons who have been exposed to radiation as released by the accident at the Chernobyl Nuclear Power Station in April 26, 1986 will be provided. The study deals with a recently assembled in-utero cohort which includes persons who were exposed to Chernobyl fallout radiation in-utero and early life and a main cohort which has been established and consists of subjects who were age 18 or under at the time of the accident, had their dose to the thyroid gland measured, and lived in the Chernobyl affected areas in Belarus.